1. Field of the Invention
The present invention relates to a developing apparatus for processing a substrate having a surface coated with a resist and processed by an exposure process, a developing method and a storage medium.
2. Description of the Related Art
A resist pattern forming process, namely, one of processes included in a semiconductor device fabricating method, forms a resist pattern by coating a surface of a semiconductor wafer (hereinafter, referred to simply as “wafer”) with a photoresist film, exposing the photoresist film in a predetermined pattern, and developing the exposed photoresist film. Generally, such a resist pattern forming process is executed by a system built by connecting a coating and developing apparatus that forms a resist film on a wafer and develops the resist film, and an exposure system.
A conventional developing process holds a wafer in a horizontal position, for example, on a substrate holding device, and disposes a developer nozzle provided with small pouring holes at a position slightly above the surface of the wafer. Then, the wafer is rotated about a vertical axis and the developer nozzle is moved along a radius of the rotating wafer, pouring a developer onto the wafer. Consequently, a spiral bead of the developer is formed on the surface of the wafer. The wafer wetted with the developer is kept stationary for a predetermined developing time, and then a rinsing solution is poured onto the surface of the wafer to rinse the developer away. This developing process is called a puddle developing process.
Use of a large quantity of developer is a drawback of the puddle developing system. Studies have been made to use a developing process mentioned in JP-A 2005-210059 (Paragraph 0044 and FIG. 5) (Patent document 1) instead of the puddle developing process. The developing process mentioned in Patent document 1 pours a developer onto a rotating substrate. This known developing process will be briefly described with reference to FIGS. 15A and 15B. A spin chuck 22, namely, a substrate holding device, coaxially holding a wafer W is rotated about a vertical axis and a developer nozzle 13 provided with a pouring slit 12 and disposed with the pouring slit 12 extended from the circumference of the wafer W toward the center of the wafer W is moved from the circumference of the wafer W toward a central part of the wafer W, pouring a developer 14 in a band-shaped flow through the pouring slit 12 to supply the developer 14 in a spiral onto the surface of the wafer W so that he surface may be coated entirely with a developer film 15. After the developer nozzle 13 has been moved to the central part of the wafer W and the wafer W has been entirely coated with the developer 14, the developer nozzle 13 continues pouring the developer 14 onto the central part of the wafer W to prevent the developer film 15 from drying. In a little while a resist pattern is developed in a resist film coating the surface of the wafer W. Then, a rinsing nozzle, not shown, pours a rinsing solution onto the surface of the wafer W to rinse the developer 14 away. Thus the developing process is completed.
The developing process that forms the developer film 15 of the developer on the wafer W by pouring the developer through the developer nozzle onto the wafer W while the wafer w is rotating can reduce the time needed to complete the developing process by moving the developer nozzle 13 at a moving speed higher than that at which the developer nozzle is moved in the puddle developing process. This developing process forms the developer film of the developer 14 on the surface of the wafer W in a thickness smaller than that of a developer film formed by the puddle developing process, which is considered to be effective in reducing the consumption of the developer 14. Some resist requires narrowing a process margin to suppress the occurrence of development defects and to form lines of a resist pattern in a satisfactory CD, namely, the width of lines of a resist pattern. Consequently, in some cases, the developing time and the quantity of the used developer needed by the developing process cannot be satisfactorily reduced. Thus the reduction of the developing time and the quantity of the developer is still a problem to be solved in the developing process.
To stabilize a developed resist pattern formed by the foregoing developing method, a time between the time the wafer W is coated entirely with the developer film 15 and the time the developer film 15 is rinsed away with the rinsing solution is in the range of 10 to 20 s. The developer may be poured at a low pouring rate such that the developer film 15 does not dry during that time. If the developer 14 is poured continuously during that time at the same pouring rate as the developing process, the developer 14 cannot be satisfactorily economized.
A pouring rate at which the developer is poured through the pouring slit 12 after coating the surface of the wafer entirely with the developer film 15 can be reduced by optionally changing a developer supply rate at which the developer is supplied through a developer supply pipe 16 to the developer nozzle 13. The developer nozzle 13 is designed such that the developer is poured through parts of the pouring slit 12 respectively at longitudinally different positions at the same pouring rate and at the same pouring pressure to pour the developer in a stable band-shaped flow as mentioned above when the developer is supplied at a predetermined flow rate to the developer nozzle 13. If the developer is supplied to the developer nozzle 13 at a flow rate lower than the predetermined flow rate, the developer 14 is poured unstably through the pouring slit 12. Consequently, normal development cannot be achieved, developing defects are produced and an irregular resist pattern is formed.
Recently, studies have been made to suppress irregularities in a developing process and to simplify piping by providing a single developing apparatus with plural developing units and using the developer nozzle 13 as a common developer nozzle for all the plural developing units instead of providing a coating and developing system with plural developing apparatuses each provided with a single developing unit including a spin chuck. Suppression of the consumption of the developer is a problem also in such a developing apparatus provided with plural developing units. Although the developing process mentioned in Patent document 1 executes several developer pouring cycles, such a developing process cannot solve the foregoing problem.